Cellular wall structure and method of making same

ABSTRACT

Cored cellular members are made from sheets or webs of paper, paperboard, corrugated board, etc. with cross walls which include portions integrally attached to spaced, opposed facing walls. The integral attachment of the cross walls to the facing walls results in a high-strength connection preventing separation of the cores from the facing walls. The cellular structures may be formed by methods which convert the sheets at high speeds and in a continuous manner.

United States Patent Martin 1.. Downs Appleton, Wis.

Feb. 26, 1969 Dec. 14, 1971 l-lammermill Paper Company lnventor Appl.No. Filed Patented Assignee CELLULAR WALL STRUCTURE AND METHOD OF MAKINGSAME 10 Claims, 7 Drawing Figs.

U.S.Cl 161/69, 161/99,161/l00.l61/102,161/104, 161/105, 161/106,161/107, 161/139, 161/160, 161/161,

Int. Cl 1332b 3/04, B321) 3/20, B32b 5/18 Field of Search 156/156,

197, 204, 209, 202, 210, 474, 512, 548; 29/191.4, 455 LM;52/615; 161/68,69,127,129,131,l35, 137, 99,139, 160, 250,102, 104, 105,106, 107

[5 6] References Cited UNITED STATES PATENTS 2,426,058 8/1947 Scogland156/148 X 3,191,724 6/1965 De Ridder 52/615X 3,264,153 8/1966 Rodman eta1 156/79 3,294,387 12/1966 Chavannes 161/127 X 3,346,438 10/1967Chavannes 156/210 Primary Examiner-John T. Goolkasian AssistantExaminer-Henry F. Epstein Attorney-Luedelta, Fitch, Even and TabinABSTRACT: Cored cellular members are made from sheets or webs of paper,paperboard, corrugated board, etc. with cross walls which includeportions integrally attached to spaced, opposed facing walls. Theintegral attachment of the cross walls to the facing walls results in ahigh-strength connection preventing separation of the cores from thefacing walls. The cellular structures may be formed by methods whichconvert the sheets at high speeds and in a continuous manner.

PATENTED 0501mm 3627'.6 23

SHEET 1 [IF 2 FIG.|

INVENTOR 88 MARTIN L. DOWNS ATTYS.

PATENTEIJ DEB I 41971 SHEET 2 OF 2 INVENTOR ATTYS.

CELLULAR WALL STRUCTURE AND METHOD OF G SAW This invention relates to acored or cellular structural member having opposed parallel facing wallswhich are spaced by and joined to interior cross walls resulting in theformation of hollow cells within the interior of the structural member.This invention also relates to a method of making such cored structuralmembers.

Cored structural elements have been used in many fields, for example, asbuilding walls, panels, pallets, door constructions, etc. Partitionwalls in buildings are cored structures when made with opposed parallelsheets of plywood separated by and secured to opposite sides of woodenstuds which are spaced from each other and serve to define cells withinthe wall. Another cored structural member is a lightweight andinexpensive door made with opposed parallel plywood sheets between whichare inserted spaced cores or headers which are glued to the plywoodsheets and serve to define hollow cells within the door. There are alsosome cored structural members used as disposable pallets having opposedfacing sheets of paperboard glued on opposite sides of internal cores ofcorrugated board or wound paper tubes.

The present invention is directed to the forming of cored structuralmembers from thin, lightweight sheets or webs of paper, paperboard orcorrugated board, although thin metal or plastic sheets might be used,and overcoming problems which have restricted the use of such coredmembers. One limiting factor to an expanded use of corrugated board,paperboard or other thin materials as a cored building wall orhighstrength uses has been the lack of sufficient strength or rigidityin the final fabricated structure. For instance, present coredstructural members are susceptible to failure with separation of theexterior walls from the core cross walls due to the overstressing at theglue lines between the cross walls and exterior walls. Another problemwith many cored members involves the expense of cutting, positioning,aligning and fastening of the various cross walls to the exterior wallsas this usually involves a number of slow speed and manual operations.

Accordingly, an object of the invention is to provide improved coredstructural members made of corrugated board, paperboard or other thinmaterials.

Other objects and advantages of the invention will become apparent whentaken in connection with the accompanying drawings in which:

FIG. 3 is a diagrammatic view of another embodiment of the invention; W7w 7 V 7 M FIGS. 4, 5 and 6 are diagrammatic illustrations of a methodof forming a cored structural member of FlGl and FIG. 7 is an end,fragmentary, cross-sectional view of a nother embodiment of theinvention. 7

Generally, as shown in the drawings for purposes of illustration, theinvention is embodied in a cored, i.e., cellular, structural member 11(FIG. 1) and a method of making such structural members in a continuousmanner by converting sheets or webs of material such as paper,paperboard, corrugated board, thin metal or plastic. As will beexplained in greater detail, the present invention involves themanufacture of structural members with paper or paperboard convertingequipment which can be operated at high speeds with a minimum of manuallabor whereby structural members can be produced at a lower cost thanhand assembled processes of the prior art. Also, the invention isdirected to providing such structural members with increased strength,and this is achieved by transferring and distributing forces to crosswalls 13 (FIG. 2) from opposite, outer facing walls 14 and 15 at largeinterior areas of the cross walls rather than, as in the prior art,across narrow glue lines located at the inner planes of the outer facingwalls. To this end, the cross walls 13 may be formed from and integrallyattached to the face walls 14 and 15, as in the embodiment of theinvention illustrated in FIG. 1, or the cross walls may include a tuckwall 17 formed from the facing sheets and extending inwardly along andfastened to the transversely extending walls of preformed cores 19, asin the embodiment of the invention illustrated in FIG. 3. By use of tuckwalls 17, the facing sheets may be secured to and about substantiallythe entire circumferential surfaces of the cores to provide wide andlarge areas of interconnection for force transmission and distribution.This is in contrast to having narrow, glue line connections between thecores and the sidewalls in the prior art at which stresses becomeconcentrated.

Referring now in detail to the several cored members and the methods ofmaking the same, the structural member 11 illustrated in FIG. 1 may beproduced by paper converting equipment of the type used to handlerelatively wide and continuously traveling paper webs moving atrelatively high speeds. For example, a pair of webs 21 and 23 (FIG. 2)of paperboard are stripped from large supply rolls (not shown) and arefed downwardly to a forming station 25 for forming the cellularstructure 11. As the webs 21 and 23 enter the forming station 25, thewebs are generally parallel to one another and are spaced on oppositesides of a series of downwardly traveling, block-shaped spacers 27, 28,29, 30, 31 and 32 which are generally rectangular in cross section andspaced from each other in the vertical direction at a gap betweenhorizontally disposed adjacent sides. The spacers 27-32 may be fastenedat the inner ends thereof to a downwardly moving, endless carrier (notshown) and may have expandable and collapsible outer walls which aremoved by either mechanically or pneumatically operated means. Acollapsing of the walls inwardly after formation of the cellularstructure will facilitate removal of the spacer from the cell.

With the sheets 21 moving downwardly and disposed against the verticalsidewalls 33 of the upper one of the spacers 27, a pair of formingplungers or blades 35 and 37 move laterally from positions spacedoutwardly of the webs 21 and 23 toward each other to engage the outersides of the respective webs generally at the location of the gapbetween the spacers 27 and 28. The right fonning blade 35 moves toengage the web 23 and forces the web 23 to travel transversely acrossthe horizontal lower face 26 of the spacer 27 into engagement with theopposite web 21 and then forces this opposite web 21 to movehorizontally outwardly. As the web 21 moves outwardly from the spacer27, it encloses and enrobes the fold being formed from the other web 23.A small guide roller 39 is disposed adjacent the lower, left-hand comerof the spacer 27 to assure that the web continues traveling down andclose to the spacer. When the right-hand forming blade 35 reaches theend of its leftward travel, it has formed an outwardly extending fold orflap 43 which is four plies thick. At this time, the blade 35 may bewithdrawn from the fold.

In a similar manner, the left-hand forming blade 37 moves rightwardly toengage first the left-hand web 21 and moves beneath the path of theright-hand former blade 35 and generally parallel to the upper face ofthe adjacent spacer 28 until in position to force the right web 23horizontally and outwardly to the right to fold about and enrobe thefold formed in the left-hand web 21. During formation of the flap 43, asmall guide roller 40 holds a portion of the web 23 against the rightvertical side of the spacer 28. After forming a four-ply flap 43, theleft-hand forming blade 37 is retracted from the fold in this flap andthe guide roller 28 is also retracted to an inoperative position.

The flaps 43 are folded upwardly by means such as rollers 47 as the webs21 and 23 and spacers 27 and 28 continue to move downward and carry theflaps 43 downward. It is preferred to adhere the flap 43 to thevertically disposed portions of the web disposed along the verticalsidewalls 33 of the spacer. The outer sides of the webs 21 and 23 may bewetted with an adhesive from glue rolls 49 and 50 so that the flaps 43may be adhered to vertical portions of the respective webs when pressedthereagainst by pressure rolls 51. On the other hand, the outer sides ofthe webs may be precoated with a heat activable adhesive for securingthe flaps 43 under heat and pressure from rotatable heated pressurerolls 51 disposed beneath the rollers 47. Alternatively, the outer sidesof the webs 21 and 23 may be precoated with a heat sealable materialsuch as a polyethylene coating for heat sealing the flaps 43 in verticalpositions under heat and pressure from the rolls 5 1.

The preferred length of the flaps 43 is generally coextensive with thevertical walls 33 of the spacers so that outer facing walls aresubstantially continuous with only slight grooves 52 indicating the endof one flap 43 and the beginning; of the next flap 43. Thus, the outervertical sides of the structural member have a five-ply thickness foreach of the longitudinal sidewalls 14 and as the sidewalls leave thesealing rollers 51. it is preferred that the flaps 43 be covered bysuitable additional cover sheets 53 and 55 which are stripped fromsupply rolls 57 and 59 and adhered to the outer plies of the flaps tocover the same and the grooves 52 between the adjacent ends of theflaps. After adherence of the cover sheets 53 and 55 to the flaps 43,the spacers are removed such as by collapsing the sidewalls 26 and 33inwardly to reduce the cross-sectional dimensions of the spacersrelative to the dimensions of the surrounding core walls and thenretracting spacers in a direction parallel to the length of the hollowcell.

From the above-described method, it will be seen that the coredstructural member 11 has four-ply cross walls 13 which are integrallyattached to the flaps 43 and the portions of the webs 21 and 23 formingthe longitudinal sidewalls 14 and 15 of the structural member. Thus,stresses applied to the structural member 11 are directly transferredand distributed between the sidewalls and the cross walls and need notbe transferred through nor concentrated at narrow glue lines as in priorart structures. As the structural member 11 was formed in a continuousmanner from several webs of paperboard, the usual costly steps of priorart methods involving alignment and placing of cores on sheets andgluing them manually between opposite facing walls have been eliminated.

When the structural member of FIG. 1 is formed of thin flexiblepaperlike material, the structural member may be collapsed to reduce itsthickness and thereby its bulk so that a greater number of structuralmembers can be stored in a given volume. Specifically, the face walls 14and 15 may be shifted in opposite directions to incline the cross walls13 to provide a parallelogram shaped cross section for the cores. Wherethe cored structural member 11 is to be used as a wall for or in abuilding, the sidewalls will be shifted in the reverse directions untilthe cross walls 13 are again disposed at the normal rectangular crosssection. For a typical building wall, the cross-sectional area of thecell will be slightly greater than that of a nominal 2X4 stud. Thus, awooden 2X4 stud may be inserted into the appropriate ones of cells andat the desired spacings for holding the facing walls 14 and 15 againstlateral shifting and for fastening the structural member 1 l in positionin the building.

For use in building construction, the webs 21 and 23 may be made of orwith a water resistant or waterproof material. For example, the webs 21and 23 may be made of a paper based material coated with a polyethylenecoating. Such a waterproof coating permits the hollow cells to be filledwith a wet aggregate, plastic foam or other material capable ofhardening, in situ, in the cells to provide rigid supports and/orcompression members for the structural member 11. Also, the sheets maybe treated or impregnated with a suitable organic fireproofing materialto increase the fire rating for the structural member.

To make the structural member 11 more rigid, reinforcing means such ascontinuous reinforcing bands or strips (not shown) of metal may befastened to the opposite faces 14 and 15 to lock the same againstshifting or pivoting relative to one ream another. it will beappreciated that various longitudinal apertures may be provided in thesheets to receive utilities, electrical wiring or other elements. Also,the cross walls may be perforated or scored to provide knockouts whichwill serve as longitudinally aligned apertures to receive such utilitylines.

The structural member 11 may also be made by precreasing each of thewebs 21 and 23 at the location of each of the fold lines defining theflaps, cross walls and vertical walls. Then the folds are erected andpositioned by suitably collapsing the web to form the cross walls 13 andflaps 43 prior to the folding and securing of the flaps 43 in place.

In accordance with another embodiment of the invention, a cellularstructural member 71 (FIG. 3) is formed with opposite, parallel facingwalls 73 and 75 attached to the internal prefonned cores 19 by the tuckwalls 17. In this instance, the preformed cores 19 are formed ofconvolutely wound sheets of polyethylene coated paper wound to provide arectangularly shaped cross-sectional hollow cell in the interiorthereof. In this instance, the preformed core 19 has three plies 81, 82and 83 bonded to each other to define a relatively rigid core. Thesepreformed cores 19 may be formed to quite close tolerances and thusprovide a structural member with good dimensional accuracy.

When making the structural member 71, the preformed cores 19 are carriedby a suitable conveyor along a path of travel such as to the right asviewed in H6. 3. Sheets 86 and 87 extend across the upper and lowerfaces respectively of the preformed cores. Forming means including apair of reciprocal blades and 88 force portions of the sheets 86 and 87inwardly into gaps between transversely extending core walls 77 andthereby form folded tuck walls 17. The forming of the tuck walls 17 maybe assisted by precreasing the sheets 86 and 87 at longitudinally spacedlocations to provide the fold lines for the tuck walls 17. Preferably,the tuck walls 17 extend inwardly to abut each other at fold lines 89positioned generally centrally of the transverse core walls 77.

The inner sides of the sheets 86 and 87 are secured, such as by anadhesive, to both the core transverse core walls 77 and to horizontallydisposed, core outer walls 90. in this illustrated structural element71, substantially the entire peripheral area of each of the cores 17 isengaged by and adhered to the sheets forming the facing walls for thestructural member. This wide area adhesion permits stresses to transferbetween the outer walls and the core walls and distributes forcesapplied to the cores over large areas thereby resulting in less forceper unit area tending to break the adhesion between the cores and thefacing walls. To cover grooves 91 at the location of the tuck walls 17,cover webs or sheets 93 and 95 are stripped from the supply rolls andsuitably bonded by an adhesive to each other to the opposite sides ofthe respective sheets 86 and 87.

The preformed convolutely wound cores 19 may be made in the manner oftubular forms for receiving concrete so that concrete, cement or otherwet and hardenable material may be poured therein and hardened, in situ.If concrete is poured in the hollow cores 19, the structural member 71functions both as a form as well as the finished structural member.lnorgarric additives may be added to the paper or other flame proofingagents may be added to the cores, the facing sheets 85 and 86 and coversheets 93 and 95 so that the concrete wall structure 71 is provided withan improved fire rating.

A further kind of cored structural element 97 is illustrated in FIG. 7and is formed with preformed cores 100 attached along their transversesides 101 to tuck walls 103 and 104. The tuck walls 103 are formed froman outer facing sheet and the other tuck walls 104 are formed from anopposite facing sheet 106. In this instance, the respective tuck walls103 and 104 extend and are bonded to an entire face of the core. Thatis, the tuck walls 103 and 104 extend the full distance between the facesheets 105 and 106 rather than meeting one another in a generallycentral plane as in the embodiment of FIG. 3.

In the structural element 97, the tuck walls 103 from the sheet 105extend the full length of a transverse core wall and alternate with thetuck walls 104 from the sheet 106 rather than having tuck walls formedfrom both sheets and inserted to meet each other as in structural member'71 illustrated in FIG. 3. To achieve good strength, the tuck walls 103and 1% are secured as by a suitable adhesive along and to the entirearea of the transverse walls 101 of the core elements Likewise, thefacing sheets 105 and 106 are adhered to the outer sides 108 of the coreelements 100. Also, the plies of the folded tuck walls 103 and 104 areadhered at an interface 107 between the plies. If it is decided to coverthe grooves existing at the location of the tuck walls 103 and 104, apair of outer cover sheets 109 may be disposed on and adhered to theouter sides of the cover sheets 105 and 106.

The preferred method of making the structural member 97 will bedescribed in connection with the illustrations in FIGS. 4, 5 and 6.Referring to FIG. 4, pairs of the core elements 100 are placed on andadhered to the facing sheet 105 with a relatively large spacing 110between the pairs of core elements, the spacing 110 being slightlygreater than twice the dimension of an outer wall 108 for the coreelements. The cores 100 are adhered at sides 101 to the facing sheet105. The latter is engaged by an upsetting or by a folding mechanism.For instance, a folding mechanism operates a folding blade 112 (P16. 5which, as viewed in this figure, engages the underside of the sheet 105at points in planes located between the closely spaced walls 108 of eachpair of core elements. As the folding blades 112 move upwardly and formthe tuck walls 103, the blades cause the core elements 100 to pivotthrough approximately 90 turning the short sides 108 of the cores 100from a generally vertical position to a substantially horizontalposition, as viewed in these figures. After the tuck wall 103 is formed,the folding blade 112 retracts, the plies of the tuck wall are abuttedat the interface 107 and are adhered together by suitable adhesive. itwill be appreciated that the cores 100 will upset from the positionillustrated in FIG. 4 to that illustrated in FIG. 6 upon application ofan upward force causing the cores 100 to pivot and that it is notnecessary to form a fold by the folding blade 112, particularly if thesheet 105 is already precreased to form a fold.

With the tuck walls 103 formed and securing the core elements atalternating positions, the other facing sheet 109 is brought over theouter, now unsecured walls 108 of the core elements and suitable tuckingblades (FIG. 6) form tuck walls 104 as the tucking blades move into thespaces left between the adjacent pairs of core elements 100. Preferably,the tuck walls 104 are also adhered to transverse walls of the coreelements 100 and along the common interface between the plies of thetuck walls 104 to provide a relatively solid and rigid cored structuralelement. Then if desired, cover sheets 109 may be disposed over theouter sides of sheets and adhered thereto.

An alternative method of forming the cored structural element 97 wouldbe to form the same generally in the manner hereinbefore described inconnection with a structural element 71 of FIG. 3 with exception thatfolding blades 85 and 88 would have a longer travel or stroke and form atuck wall extending substantially the full length of the transverse corewall. Also, the folding blades would be inserted alternatively ratherthan simultaneously to form a tuck wall at each spacing between thecores.

From the foregoing, it will be seen that cored structural elements maybe made from a number of relatively thin and flexible materials withcross walls defining cores or spaces within the interior of the coredstructural member providing rigidity and strength to the coredstructural member. The cross or tuck wmls may be integrally formed fromthe sheets forming the face walls or may serve to provide largeadditional interior areas of contact with preformed core elements. Ineither event, there is a considerable area of contact between the coreelements and the facing walls and particularly within the interior ofthe core element so that stress concentrations are applied moreuniformly throughout the product than is the case with prior artstructural elements in which only an outer side or face of the preformedcore element was attached to facing sheets at glue lines which tended toconcentrate stresses resulting in ultimate failure in some instances. Asseen from the foregoing, cored structural elements may be made withrelatively high-speed paper converting machinery thereby eliminating theusual assembly and alignment of large numbers of preformed cores.

While a preferred embodiment has been shown and described, it will beunderstood that there is no intent to limit the invention by suchdisclosure, but rather, it is intended to cover all modifications andalternate constructions falling within the spirit and scope of theinvention as defined in the appended claims.

What is claimed is:

1. A cellular structure comprising means including a first sheet ofcellulosic material defining a first face wall for said cellularstructure, means including a second sheet of cellulosic materialdisposed parallel to and spaced from said first sheet and defining asecond face wall, fold lines in each of said first and second sheets,cross walls formed from each of said sheets and integrally attached tosaid face walls at said fold lines, said cross walls extending betweensaid face walls and dividing the space between said face walls into aseries of hollow cells, each of said cross walls being a multi-ply wallwith the plies thereof in face to face engagement.

2. A cellular structure in accordance with claim 1 in which the crosswalls are formed with at least four plies, two plies of which are formedfrom each of said first and second sheets and in which said cross wallsare disposed substantially normal to the facing walls.

3. A cellular structure in accordance with claim 1 in which hollowpreformed tubular members are fastened along first sides thereof to saidfacing walls and along other sides thereof to said cross walls.

4. A cellular structure in accordance with claim 3 in which said hollowpreformed tubular members are formed of multiply sheets, said tubularmembers having first and second pairs of parallel sidewalls.

5. A cellular structure in accordance with claim 4 in which said crosswalls of said sheets extend inwardly and meet substantially centrally inthe space between said sheets and each are fastened to at least one ofsaid parallel sidewalls of said hollow preformed members.

6. A cellular structure in accordance with claim 4 in which said crosswalls extend substantially across the space between said sheets and inwhich cross walls formed from one sheet alternate with the cross wallsformed from the other sheet, each of said cross walls abutting andsecured to a pair of adjacent hollow tubular members.

7. A cored structural member comprising a first sheet of cellulosicmaterial defining a first face wall for said cored structural member, asecond sheet of cellulosic material defining a second face wall disposedin a plane generally parallel to and spaced from said first face wall, aplurality of hollow cores inserted into the space between said first andsecond facing walls and having faces abutted against and secured to therespective first and second face walls, fold lines in each of said firstand second sheets and tuck walls formed from and integrally attached toat least one of said facing walls at said fold lines and extendinginwardly from the plane thereof, said tuck walls abutted against andfastened to sides of said hollow cores.

8. A cored structural member in accordance with claim 7 in which saidhollow cores are preformed and have opposed pairs of parallel sidewalls,and in which said tuck walls are formed in both of said face sheets andextend inwardly toward one another along the core sidewalls extendingtransversely of the face sheets.

9. A cored structural member formed of a first and second web ofcellulosic material, said cored structural member including spacedparallel facing walls each comprised of a series of flaps each havingmultiple plies of said first and second webs, and fold lines in saidfirst and second webs and cross in which folded plies of one web areenrobed by the other web at a flap in one facing wall and in which thefolded plies of the other web are enrobed with said one web at a flap inthe other facing wall.

2. A cellular structure in accordance with claim 1 in which the crosswalls are formed with at least four plieS, two plies of which are formedfrom each of said first and second sheets and in which said cross wallsare disposed substantially normal to the facing walls.
 3. A cellularstructure in accordance with claim 1 in which hollow preformed tubularmembers are fastened along first sides thereof to said facing walls andalong other sides thereof to said cross walls.
 4. A cellular structurein accordance with claim 3 in which said hollow preformed tubularmembers are formed of multi-ply sheets, said tubular members havingfirst and second pairs of parallel sidewalls.
 5. A cellular structure inaccordance with claim 4 in which said cross walls of said sheets extendinwardly and meet substantially centrally in the space between saidsheets and each are fastened to at least one of said parallel sidewallsof said hollow preformed members.
 6. A cellular structure in accordancewith claim 4 in which said cross walls extend substantially across thespace between said sheets and in which cross walls formed from one sheetalternate with the cross walls formed from the other sheet, each of saidcross walls abutting and secured to a pair of adjacent hollow tubularmembers.
 7. A cored structural member comprising a first sheet ofcellulosic material defining a first face wall for said cored structuralmember, a second sheet of cellulosic material defining a second facewall disposed in a plane generally parallel to and spaced from saidfirst face wall, a plurality of hollow cores inserted into the spacebetween said first and second facing walls and having faces abuttedagainst and secured to the respective first and second face walls, foldlines in each of said first and second sheets and tuck walls formed fromand integrally attached to at least one of said facing walls at saidfold lines and extending inwardly from the plane thereof, said tuckwalls abutted against and fastened to sides of said hollow cores.
 8. Acored structural member in accordance with claim 7 in which said hollowcores are preformed and have opposed pairs of parallel sidewalls, and inwhich said tuck walls are formed in both of said face sheets and extendinwardly toward one another along the core sidewalls extendingtransversely of the face sheets.
 9. A cored structural member formed ofa first and second web of cellulosic material, said cored structuralmember including spaced parallel facing walls each comprised of a seriesof flaps each having multiple plies of said first and second webs, andfold lines in said first and second webs and cross walls having at leastfour plies which are integrally connected to and formed from said firstand second webs, said cross walls joined to said flaps at said foldlines and extending transversely between said facing walls and dividingthe spaces therebetween into cells.
 10. A cored structural member inaccordance with claim 9 in which folded plies of one web are enrobed bythe other web at a flap in one facing wall and in which the folded pliesof the other web are enrobed with said one web at a flap in the otherfacing wall.